This invention relates to geothermal fluids and in particular to an apparatus for measuring noncondensible gas flow relative to steam flow in such fluids.
Geothermal fluids contain noncondensible gases. The concentrations of such noncondensible gases in geothermal fluids produced through geothermal wells vary. These gases can include hydrogen sulfide, carbon dioxide, ammonia and other gases some of which may appear as so-called pollutants when discharged to the atmosphere in quantity. The ratio of noncondensible gases to steam is an important parameter in geothermal reservoir evaluation, resource management, power plant design and operation, and compliance with environmental regulations.
For example, where such geothermal fluid is being used in combination with a turbine exhausted to a condenser, the presence and concentration of noncondensible gases in the flow creates a gas discharge problem which must be specifically met. In order to realize efficiency, turbine exhaust to a condenser from geothermal fluids must be below atmospheric pressure. Consequently, noncondensible gases must be ejected from below atmospheric pressure. Moreover, gas ejection equipment must be precisely sized and designed.
Where gas is encountered above that level for which ejection equipment is designed, the temperature in the condenser rises, back pressure in the condenser likewise rises and the load can be lost.
Conversely, where gas is present at a level below the design of noncondensible gas ejection equipment, steam in the low pressure turbine can go to sonic levels. When this occurs, the temperature then rises with loss of efficiency and danger of loss of load.
Furthermore, the presence and kind of noncondensible gases must be known. Specifically, and where a geothermal plant "starts up," provision must be made to eject the gases during the start up. Moreover, since some of the gases present are rated as atmospheric pollutants, accurate measurement of their presence is now required by regulation. Obtaining and maintaining an accurate measurement of the gases present is necessary to determine what type and quantity of treatment should be rendered to the gas.
Additionally knowledge of the presence and kind of noncondensible gases in geothermal fluids from individual wells is essential for the evaluation and management of a geothermal reservoir. Noncondensible gas/steam ratios and noncondensible gas composition are used, with other information, to determine reservoir temperatures and fluid reserves, as components in physiochemical reservoir modeling, to plan resource exploitation to comply with environmental regulations and power plant design limitations, and for other important operations in reservoir evaluation and management.